Hellerup, Denmark, 10 January 2023 – UNION therapeutics A/S (UNION), a privately-held, multi-asset, clinical stage, pharmaceutical development company focused on immunology and infectious disease, today announced that the US Food and Drug Administration (FDA) has granted Fast Track designation to oral orismilast for the treatment of moderate to severe HS. The FDA’s Fast Track designation is intended to facilitate the development and review of drug candidates that treat serious conditions and address a significant unmet medical need. A drug candidate that receives Fast Track designation is eligible for more frequent interaction with the FDA to discuss the drug candidate’s development plan as well as eligibility for rolling review and priority review.  

In the coming interactions with FDA, UNION plans to discuss the most appropriate endpoints, target disease severity, and next steps in the clinical development of oral orismilast for the treatment of HS.

In September, the Danish Medicines Agency and Ethics Committee granted a Treatment Extension to the ongoing investigator-led study of oral orismilast (OSIRIS, Phase 2a)1) for the treatment of patients with mild to severe HS. With the Treatment Extension, patients who have completed the initial treatment period in the OSIRIS study may continue treatment with orismilast MR tablets for a period of 52 weeks.

Professor Gregor B. Jemec, PhD, MD, Founding Chairman of the Department of Dermatology, Zealand University Hospital Roskilde, Denmark said:

Hidradenitis suppurativa is an inflammatory systemic skin disease that seriously affects the life of patients. Despite the recent advances in the treatment of hidradenitis suppurativa, there is still a high unmet need in terms of safe and efficacious oral treatments. It is encouraging to see that FDA recognizes the potential of oral orismilast in hidradenitis suppurativa and grants it fast track designation.”

Kim Kjøller, Chief Executive Officer of UNION therapeutics said:

We are very pleased to receive this Fast Track designation for oral orismilast in hidradenitis suppurativa (HS) and look forward to working closely with the FDA in the design of the clinical development program for oral orismilast. Our ambition is to provide an effective oral treatment for HS and in collaboration with dermatologists and patients develop relevant trial designs, addressing the true needs of patients living with HS.”

About orismilast

UNION is developing orismilast, a high-potency PDE4 inhibitor targeting the PDE4 subtypes linked to inflammation. It operates early in the inflammation cascade, inducing a broad range of anti-inflammatory effects across multiple cytokines involved in many dermatological and immunological diseases. 2)

Orismilast holds the potential to become a safe and efficacious oral treatment for many immunological diseases, and UNION is currently developing oral orismilast for the treatment of AD, psoriasis, and HS.

The FDA has cleared UNION’s Investigational New Drug (IND) application for oral orismilast and granted Fast Track designation for oral orismilast for the treatment of moderate to severe AD as well as for the treatment of moderate to severe HS. In 2021, UNION entered a strategic partnership with Innovent Biologics for the development of orismilast in Mainland China, Hong Kong, Macau, and Taiwan.

About HS and treatment of HS

HS is a chronic, progressive, inflammatory skin disease that usually develops after puberty as a result of inflamed hair follicles, most notably in the armpit and genital regions. The clinical hallmarks of the disease include very painful inflammatory nodules, boils or abscesses that typically open and release odorous inflammatory fluids. As HS progresses, the scars form tunnels or sinus tracts that connect. HS patients suffer primarily from pain and significant discomfort as a result of the constant formation of pus, and often require the use of bandages, resulting in social isolation. Many patients are stigmatized by these symptoms, leading to a very diminished quality of life. HS is associated with various more general diseases, such as arthritis and metabolic syndrome.

Currently, there is only one drug approved for the treatment of moderate to severe HS, which is a biologic administered through injections. For mild HS there are no treatments approved. The general standard of care for HS patients, although off-label, includes topical antiseptics and oral antibiotic treatment which often provide only temporary symptomatic relief. Antibiotics do not target the underlying inflammation and they are associated with resistance development. 3)



1)      Taudorf E.H. and Jemec G.B. OSIRIS – Orismilast for the Treatment of Mild to Severe Hidradenitis Suppurativa: Rationale and Design.11th Conference of the European Hidradenitis Suppurativa Foundation. 2022 Feb 9-11. PV-05-02 and

Taudorf E.H. et al. Rapid reduction of inflammation in severe hidradenitis suppurativa following treatment with the PDE4-inhibitor Orismilast, oral presentation at 11th Conference of the European Hidradenitis Suppurativa Foundation. 2022 Feb 9-11

2)      Silverberg J.I. et al., Pharmacology of orismilast, a potent and selective PDE4 inhibitor, JEADV 2022: https://onlinelibrary.wiley.com/doi/10.1111/jdv.18818  &

Warren R.B. et al., Efficacy and safety in moderate-severe psoriasis and development of modified release tablets, JEADV 2022: https://onlinelibrary.wiley.com/doi/10.1111/jdv.18812

3)      Saunte D.M.L. and Jemec G.B., JAMA 2017: https://pubmed.ncbi.nlm.nih.gov/29183082/



Morten Boesen, Chief Financial Officer, UNION therapeutics A/S

+45 2381 5487

[email protected]

Sarah Toft-Jørgensen, Director of Communications and IR, UNION therapeutics A/S

+45 5385 3044

[email protected]


About UNION therapeutics

UNION therapeutics is a privately held, multi-asset, clinical stage, pharmaceutical development company focused on immunology and infectious diseases. The company is currently working with two complementary chemistry classes, spanning immunology and microbiology with multiple candidates in clinical development. UNION is headquartered in Hellerup, Denmark, and led by an international team combining biotech entrepreneurs and seasoned pharma executives, with a track record of developing and launching more than fifteen marketed drugs. Read more at http://www.uniontherapeutics.com